Forecasting prospective market levels out 12 months is an imprecise art form that requires probabilistic decision making, using imperfect information about an inherently unknowable future.

Forecasting market levels out beyond 12 months is, to me, more a function of one's philosophy than an investment prediction.

But try we must (especially over the next 12 months) even despite The Oracle's protestations.

It has been nearly nine months since I last published my estimate of the S&P 500's fair market value, but I am going to give it a go again this morning (with the insistence from subscriber Renato, who sent me a nice note recently).

Remembering the phrase that if you have to forecast, forecast often, I will attempt to update my fair market value every month or as circumstances change.

Early this year, I expressed the view that a domestic economy incapable of reaching escape velocity would produce a challenging earnings landscape. This, to me, represented the principal enemy to the U.S. stock market for 2013 and formed the basis for my four core scenarios (economic, earnings and market valuation) that yielded my fair market value calculation.

Anemic top- and bottom- line growth in corporate sales and profits were by no means the only factors that contributed to my valuation concerns this year as was the growing evidence that aggressive monetary policy is losing its effectiveness and that our leaders are failing to address our deep-seated fiscal issues. Instead (and out of necessity), our authorities placed ever more pressure on our monetary policymakers to bear the responsibility of bringing our domestic economy out of its doldrums. After nearly five years, the results barely met a passing grade and uncovered the depth of our structural headwinds that have been ignored for so many years (e.g., disequilibrium in the jobs market, screwflation of the middle class, financial repression penalizing the savings class, etc.), and once again, the Fed has overestimated U.S. economic growth and the positive impact of trickle-down economics (through the lifting of asset prices).

Forecasting is the art of saying what will happen and then explaining why it didn't. While my fundamental observations (and headwinds) still seem materially correct, my assumptions for a contraction in P/E multiples were wrong-footed as were my market conclusions and S&P price targets.

This year, the S&P 500 dramatically eclipsed my calculations of fair market value, owing to both an expansion in P/E multiples and a better corporate profit performance. (One third of the S&P's better rise was due to higher profits and two thirds was due to an expansion in multiples.)

A year ago, my baseline expectation for 2013 S&P profits was between $100 and $102 a share.

Today, as we near year-end, the consensus estimate for 2013 S&P earnings is $109 a share. I am now at a below-consensus forecast of between $107 and $109 a share.

For 2014, the consensus estimates that the S&P 500 will achieve profits of about $116 to $118 a share. My base case estimate is for $112 to $114 a share, a gain of under 5% (year over year), which is, again, below consensus.

Slowing sales, a contraction in margins, the reduced influence/benefit from aggressive monetary policy and political uncertainties are some of the reasons why my baseline earnings expectation are for below-consensus 2014 S&P 500 profits.

reflecting the continued and surprisingly low-interest-rate environment, I have increased the P/E ratios applied to each of the four outcomes from my previous fair market value calculation; and

profit forecasts for 2013-2014 have been revised upward to reflect what has been reported and earned thus far in 2013.

Since I began this exercise several years ago, I have tried to be consistent with methodology, reasonable in my profit forecasts, and I have applied sensible valuations. Again, I want to emphasize that my methodology, though appearing precise, recognizes the difficulty of attaining investment precision given the numerous moving parts (economic, interest rates, sentiment/psychology, political outcomes and other exogenous factors) in its calculation. It is intended more as a thoughtful guideline (of reasonable expectations/outcomes) than an exercise that should be taken literally. (I strongly recommend that subscribers input their own probabilities and outcomes in order to produce their own market expectations.)

Scenario Analysis

"A good forecaster is not smarter than everyone else; he merely has his ignorance better organized."

-- Anonymous

Below are the criteria and methodology I use to evaluate the S&P 500 and upon which I conclude that fair market value is approximately 1645 (it is overvalued by about 5% compared to Friday's close of 1740).

Scenario No. 2 -- Near-Recession (15% probability): The U.S. enters a near-recession (zero to +1.5% real GDP). The Fed extends quantitative easing throughout the year, but it becomes clear that monetary policy has lost its effectiveness. The eurozone turns back into negative real GDP growth, and the debt crisis renews. China's real GDP falls below +7%. The Democratic and Republican Parties grow more contentious, partisan and unequivocal in position. The sovereign debt crisis in Europe heats up again, contributing to a deepening European recession and a hard landing in China and India. The yield on the 10-year U.S. note dips below 2% again. S&P 500 earnings estimates for 2014 are materially reduced (relative to consensus expectations) to a range between $95 and $100 per share. Stocks, valued at 14x under this outcome, have 22% downside risk over the next 12 months. S&P target 1365.

Scenario No. 3 -- Below-Consensus Economic Growth (50% probability): The U.S. experiences a disappointing +1.5% real GDP growth rate, Europe experiences little recovery (zero to +1.0% real GDP), and China's economic growth modestly disappoints relative to expectations. The Fed announces a plan to extend its QE program and doesn't taper in 2014. The yield on the 10-year U.S. note is held between a range of 2.25% and 2.75%. The S&P 500 consensus profit forecast for 2014 is too high ($110 to $112 per share is expected), as corporations' pricing power is limited and profit margins are pressured more than expected. Stocks, valued at 14.75x under this outcome, have 6% downside risk over the next 12 months. S&P target 1635.

Scenario No. 4 -- Muddle Through (30% probability): The U.S. muddles through, with 2.0% to 2.5% real GDP growth; the European economies post a modest recovery (+1% real GDP); and China's economy grows in line relative to consensus forecasts. The Fed's tapering begins in March 2014. The yield on the 10-year U.S. note is between 2.75% and 3.25%. S&P 500 profits for 2014 are in the range of $112 to $114 a share as some modest margin slippage occurs. Stocks, valued at 15.5x under this outcome, are now fairly priced. S&P target 1750.

Whether one is gazing at charts or incorporating fundamentally based discount models, all too often technical and fundamental analysts proclaim precision of market forecast. Frankly, I view those pronouncements as laughable.

There is no special sauce, fractal or system to beat the market and to forecast its future with consistent accuracy -- if there was, Steve Cohen, George Soros or Paul Tudor Jones would have purchased the recipe.

I use this morning's exercise as a guide to portfolio management. Again, it is certainly not meant to be an exercise in precision, but I have found this calculation, over time, to be a generally good discipline that keeps me honest.

The Market Is Moderately Overvalued

The line separating investment and speculation, which is never bright and clear, becomes blurred still further when most market participants have recently enjoyed triumphs. Nothing sedates rationality like large doses of effortless money. After a heady experience of that kind, normally sensible people drift into behavior akin to that of Cinderella at the ball. They know that overstaying the festivities -- that is, continuing to speculate in companies that have gigantic valuations relative to the cash they are likely to generate in the future -- will eventually bring on pumpkins and mice. But they nevertheless hate to miss a single minute of what is one helluva party. Therefore, the giddy participants all plan to leave just seconds before midnight. There's a problem, though: They are dancing in a room in which the clocks have no hands.

-- Warren Buffet's letter to Berkshire Hathaway shareholders, 2000

I continue to see the stock market as being moderately overvalued -- the higher we go from here, the line between speculation and investment seems likely to be increasingly blurred.

In the past, I have suggested that in a 5% overvalued market, a conservative investor should not be more than 50% long -- and I still stand behind that.

So, if I believe (as I currently do) that the market is slightly more than 5% overvalued, why have any investments in equities?

The answer is obvious.

At any given time (regardless of where the market is selling), individual stocks are overvalued and undervalued. This is particularly true today since there is so much uncertainty in fiscal (and monetary) policy, in political/economic outcomes and with regard to business and consumer reaction to policy.

Don't take my word for the fair market value calculation. Again, I strongly encourage you to input your own earnings/economic/multiple expectations and create your own fair market value calculation.

This allows investors and traders to pick sides on the issues and make their bets a bit more intelligently, particularly on the broader market.

I hope you find this exercise to be helpful as a guideline.

This column originally appeared on Real Money Pro at 8:24 a.m. EDT on Oct. 21.

At the time of publication, Kass and/or his funds were short SPY and BRK.B, although holdings can change at any time.

Doug Kass is the president of Seabreeze Partners Management Inc. Under no circumstances does this information represent a recommendation to buy, sell or hold any security.